My ability to spew bs has allowed me many girlfriends I never should have had. And I thank you.

Excellent answer
Poorly Lived and Poorly Died, Poorly Buried and No One Cried

You have to realize, considering space travel and flight times, to achieve light speed, or faster than, the aliens change their atomic structure. Their atoms move slower, so they appear see through. Being this way, it allows them to be lighter in weight along with the ship itself to achieve lift offs from planets with greater gravity.